Novel phosphanegold(I) cluster cations combined with polyoxometalate (POM) anions, i.e., intercluster compounds, [(Au{P(m-FPh)3})4(μ4-O)]2[{(Au{P(m-FPh)3})2 (μ-OH)}2][α-PMo12O40]2•EtOH (1), [(Au{P(m-FPh)3})4(μ4-O)]2[α-SiMo12O40]•4H2O (2), [(Au{P(m-MePh)3})4(μ4-O)]2[α-SiM12O40] (M = W (3), Mo (4)) and [{(Au {P(p-MePh)3})4(μ4-O)}{(Au{P(p-MePh)3})3(μ3-O)}][α-PW12O40] (5) were synthesized by POM-mediated clusterization, and unequivocally characterized by elemental analysis, TG/DTA, FT-IR, X-ray crystallography, solid-state CPMAS 31 P NMR and solution (1 H, 31 P{ 1 H}) NMR. Formation of the these gold(I) cluster cations was strongly dependent upon the charge density and acidity of the POMs, and the substituents and substituted positions on the aryl group of triarylphosphane ligands. These gold(I) cluster cations contained various bridged-oxygen atoms such as μ4-O, μ3-O and μ-OH groups.

Novel intercluster compounds consisting of pentakis[(triphenylphosphane)gold]ammonium(2+) cation (1) and Keggin polyoxometalate (POM) anions, i.e., {[Au(PPh)](μ-N)}[α-PMO] (1-PW for M = W; 1-PMo for M = Mo), were synthesized in 30-36% yield by one-pot reaction of the protonic acid form of the Keggin POMs, H[α-PMO]·nHO (n = 13 for M = W; n = 15 for M = Mo) with monomeric (triphenylphosphane)gold(I) carboxylate [Au(RS-pyrrld)(PPh)] [RS-Hpyrrld = (RS)-2-pyrrolidone-5-carboxylic acid] in the presence of aqueous NH at a molar ratio of 2:15:x (x = 3 for 1-PW; x = 7.5 for 1-PMo). These compounds resulted from the nitrogen-centered phosphanegold(I) clusterization of in situ generated monomeric phosphanegold(I) units, [Au(PPh)] or [Au(L)(PPh)] (L = NH or solvent), during the carboxylate elimination of [Au(RS-pyrrld)(PPh)] in the presence of the Keggin POMs and aqueous NH. The products 1-PW and 1-PMo were characterized by elemental analysis, Fourier transform infrared, thermogravimetric and differential thermal analyses (TGA/DTA), X-ray crystallography, and solid-state cross-polarization magic-angle-spinning (CPMAS) (P and N) and solution (P{H} and H) NMR spectroscopy. The lattice contained three independent {[Au(PPh)](μ-N)} cations, of which two took regular trigonal-bipyramidal (TBP) geometries and the third took a distorted, square-pyramidal (SP) geometry. These geometries are in contrast to those reported by Schmidbaur's group for {[Au(PPh)](μ-N)} cations as BF salts. Density functional theory and ONIOM calculations for {[(LP)Au]N} (L = H or Ph; n = 4-6) showed that the pentacoordinate cluster is energetically most stable and its TBP structure is only 1.6 kcal mol more stable than its SP structure, in accordance with the experimental facts.

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